Diethyl L-tartrate Research Articles

Hydrogen-bond-assisted asymmetric radical cyclopolymerization of N-allyl-N-tert-butylacrylamide in the presence of chiral tartrates

Low-temperature radical polymerization of achiral N-allyl-N-tert-butylacrylamide (AltBAAm) was conducted in toluene in the presence of chiral tartrates, such as diethyl l-tartrate (L-EtTar) and di-n-butyl l-tartrate. The 1H NMR spectra of the polymers obtained indicated progress of cyclopolymerization at low temperatures such as −80 °C. Optical properties of the poly(AltBAAm)s examined by optical rotation and circular dichroism measurements indicated asymmetric induction in the cyclopolymerization of achiral AltBAAm. For example, addition of L-EtTar at −80 °C provided the polymer with specific rotation of −4.8°. The tert-butyl groups of poly(AltBAAm)s were removed by treatment with CF3SO3H, transforming into poly(N-allylacrylamide)s [poly(AlAAm)s]. Then, stereochemistry in the stereorepeating unit was investigated by comparing 1H NMR signals of the poly(AlAAm)s with those of model compounds, cis- and trans-3-ethyl-4-methyl-2-pyrrolidones. Taking the negative specific rotation values of the poly(AltBAAm)s obtained with L-tartrates into account, it was revealed that (3S,4S)-trans-unit was predominantly formed through the hydrogen-bond-assisted complex formation of AltBAAm with L-tartrates.

Enantioseparation of Cinacalcet, and its Two Related Compounds by HPLC with Self-Made Chiral Stationary Phases and Chiral Mobile Phase Additives

Background:Cinacalcet is one of the second-generation calcimimetics which consists of a chiral center. The pharmacological effect of R-cinacalcet is 1000 times greater than that of the Scinacalcet. As mentioned in many literatures, 1-(1-naphthyl)ethylamine is used as the starting material for the synthesis of cinacalcet. The absolute structure of cinacalcet is influenced by the starting materials.Methods:We present the chiral separation of cinacalcet and its starting material, 1-(1-naphthyl) ethylamine along with one of its intermediates, N-(1-(naphthalen-1-yl) ethyl)-3- (3-(trifluoromethyl) phenyl) propanamide by high-performance liquid chromatography with chiral stationary phase and chiral mobile phase additives.Results:On vancomycin and cellulose tri 3,5-dimethylphenylcarbamate) chiral stationary phase, cinacalcet and 1-(1-naphthyl)ethylamine achieved enantioseparation under normal phase with addition of triethylamine additives, respectively. Meanwhile, 1-(1-naphthyl)ethylamine and N-(1-(naphthalen-1- yl)ethyl)-3-(3-(trifluoromethyl) phenyl) propanamide achieved enantioseparation on 1-napthalene vancomycin chiral stationary phase using D-tartaric acid, diethyl L-tartrate and diethyl D-tartrate as chiral mobile phase additives.Conclusion:The chiral recognition in our experiment was based on the hydrogen-bonding, dipoledipole and π-π interactions among the solutes, chiral stationary phases and chiral mobile phase additives. In addition, the space adaptability of chiral stationary phases also affected the separation efficacy.

Stereoselective synthesis of the lichen metabolite, (+) montagnetol and its congeners as antimicrobial agents

In view of structural diversity, (+) montagnetol, the major metabolite of the fruticose lichen, Roccella montagnei was synthesized along with three of its congeners by employing highly efficient protocols. (+) Montagnetol (2 R, 3S; 11) and (-) montagnetol (2S, 3R; 5) were synthesized in 7 and 9 steps, respectively, from L-ascorbic acid. The two new congeners 3 (2 R, 3R) and 6 (2S, 3S), which differ in configuration at C-2 and C-3 positions of the (+) montagnetol, were synthesized from (−) diethyl D-tartrate and (+) diethyl L-tartrate, respectively. The synthesized compounds were evaluated in vitro for antimicrobial activity against two Gram-positive (S. aureus and E. coli) and two Gram-negative (S. typhi and P. aeruginosa) bacteria and one fungal strain Candida albicans. Interestingly, the congener 3 showed promising anti-bacterial activity (MIC: 0.062 µg/ml) against P. aeruginosa, whereas the congener 6 displayed potent anti-fungal activity (MIC: 0.062 µg/ml) against C. Albicans.

Synthesis of l-threitol-based crown ethers and their application as enantioselective phase transfer catalyst in Michael additions.

A few new l-threitol-based lariat ethers incorporating a monoaza-15-crown-5 unit were synthesized starting from diethyl l-tartrate. These macrocycles were used as phase transfer catalysts in asymmetric Michael addition reactions under mild conditions to afford the adducts in a few cases in good to excellent enantioselectivities. The addition of 2-nitropropane to trans-chalcone, and the reaction of diethyl acetamidomalonate with β-nitrostyrene resulted in the chiral Michael adducts in good enantioselectivities (90% and 95%, respectively). The substituents of chalcone had a significant impact on the yield and enantioselectivity in the reaction of diethyl acetoxymalonate. The highest enantiomeric excess (ee) values (99% ee) were measured in the case of 4-chloro- and 4-methoxychalcone. The phase transfer catalyzed cyclopropanation reaction of chalcone and benzylidene-malononitriles using diethyl bromomalonate as the nucleophile (MIRC reaction) was also developed. The corresponding chiral cyclopropane diesters were obtained in moderate to good (up to 99%) enantioselectivities in the presence of the threitol-based crown ethers.

A facile approach for the total synthesis of neurotrophic diyne tetraol petrosiol A and petrosiol E

The first total synthesis of neurotrophic diacetylenic tetraol, petrosiol A and stereoselective total synthesis of petrosiol E was accomplished. The total synthesis involves Cadiot-Chodkiewicz coupling reaction as the key step for petrosiol A. The diastereorich chiral alcohol (third chiral center) was synthesized from CBS mediated stereoselective ketone reduction reaction for petrosiol E. Of the three chiral centers, the two chiral centers are originated from (+)-diethyl l-tartrate and the third chiral center was generated by an addition reaction of lithium trimethylsilylacetylide leading to two diastereomers which were used for the synthesis of both the natural products and their diastereomer C6-epi-petrosiol A and C6-epi-petrosiol E, respectively.

A facile approach for the synthesis of C13-C24 fragments of maltepolides A, C and D.

A linear, chiron approach for the synthesis of C13-C24 fragments of cytostatic maltepolides A, C and D consisting of a tetrahydrofuran subunit and a chiral alkenyl/alkyl substituent is achieved from (+)-diethyl l-tartrate. The other chiral stereocenters were generated by employing key reactions such as Crimmins aldol, alkynylation and CeCl3·7H2O mediated Luche reduction reactions.

Stereoselective total synthesis of the antiplasmodial resorcylic acid lactone paecilomycin F

A facile and convergent approach for the total synthesis of 14-membered resorcylic acid lactone paecilomycin F is described. The synthesis emanates from the readily available inexpensive (+)diethyl L-tartrate. Mitsunobu etherification, Stille coupling and ring-closing metathesis are key steps in the synthesis.

Modified Ta/MCM-41 catalysts for enantioselective oxidation of thioanisole

Ta-MCM41 catalysts have been prepared by grafting of Ta(OEt)5 on MCM41, pre-calcined at three different temperatures (550, 650 and 750°C). These solids have been modified with two chiral ligands: R-(+)-diethyl l-tartrate (DET) and R-(+)-diisopropyl l-tartrate (DIPT). The formation of the chiral tantalum species and their influence on the structure of MCM41 have been studied by several characterization techniques, such as XRD, FTIR, N2 adsorption isotherms and MAS NMR. The grafted tantalum species are always much less active than the homogeneous analogues in the oxidation of thioanisole (methyl phenyl sulfide) with either aqueous H2O2 or alkyl (tert-butyl, TBHP, or cumyl, CHP) hydroperoxides. The enantioselectivities obtained with the heterogeneous catalysts are also always lower than those obtained with the homogeneous ones under the same conditions, and the best results are obtained with the DIPT-modified solids, up to 25% ee. The calcination temperature of the support and the nature of the oxidant are also parameters that significantly affect the enantioselectivity. The recovered catalysts show an increase in the catalytic activity and a decrease in the enantioselectivity, in agreement with a loss of chiral tartrate, whereas the SiOTa bond remains stable and recoverable.

Hydrogen-bond-assisted isotactic-specific radical polymerization of N-vinyl-2-pyrrolidone with tartrate additives in toluene at low temperatures: high-resolution 1H NMR analysis

Isotactic-rich poly(N-vinyl-2-pyrrolidone) was successfully prepared by radical polymerization of N-vinyl-2-pyrrolidone assisted by diethyl l-tartrate (l-EtTar) at low temperatures.

ChemInform Abstract: Development of Tartaric Acid Derived Chiral Guanidines and Their Application to Catalytic Enantioselective α‐Hydroxylation of β‐Dicarbonyl Compounds.

A novel library of chiral guanidines featuring a tartaric acid skeleton was developed from diethyl l-tartrate. These guanidines are easily accessed with tunable steric and electronic properties. The utilities of the guanidines were highlighted by their ability to catalyze the α-hydroxylation of β-ketoesters and β-diketones with remarkable efficiency and excellent enantioselectivity.

Development of Tartaric Acid Derived Chiral Guanidines and Their Application to Catalytic Enantioselective α-Hydroxylation of β-Dicarbonyl Compounds

A novel library of chiral guanidines featuring a tartaric acid skeleton was developed from diethyl l-tartrate. These guanidines are easily accessed with tunable steric and electronic properties. The utilities of the guanidines were highlighted by their ability to catalyze the α-hydroxylation of β-ketoesters and β-diketones with remarkable efficiency and excellent enantioselectivity.

Development of diacyltetrol lipids as activators for the C1 domain of protein kinase C

The protein kinase C (PKC) family of serine/threonine kinases is an attractive drug target for the treatment of cancer and other diseases. Diacylglycerol (DAG), phorbol esters and others act as ligands for the C1 domain of PKC isoforms. Inspection of the crystal structure of the PKCδ C1b subdomain in complex with phorbol-13-O-acetate shows that one carbonyl group and two hydroxyl groups play pivotal roles in recognition of the C1 domain. To understand the importance of two hydroxyl groups of phorbol esters in PKC binding and to develop effective PKC activators, we synthesized DAG like diacyltetrols (DATs) and studied binding affinities with C1b subdomains of PKCδ and PKCθ. DATs, with the stereochemistry of natural DAGs at the sn-2 position, were synthesized from (+)-diethyl L-tartrate in four to seven steps as single isomers. The calculated EC(50) values for the short and long chain DATs varied in the range of 3-6 μM. Furthermore, the fluorescence anisotropy values of the proteins were increased in the presence of DATs in a similar manner to that of DAGs. Molecular docking of DATs (1b-4b) with PKCδ C1b showed that the DATs form hydrogen bonds with the polar residues and backbone of the protein, at the same binding site, as that of DAG and phorbol esters. Our findings reveal that DATs represent an attractive group of C1 domain ligands that can be used as research tools or further structurally modified for potential drug development.

Total Synthesis of Broussonetine F: The Orthoamide Overman Rearrangement of an Allylic Diol

A first total synthesis of broussonetine F from diethyl L-tartrate was achieved. The cornerstone of our synthesis was an orthoamide Overman rearrangement, which provided an allylic amino alcohol with complete diastereoselectivity.

Development of Chiral Terminal-Alkene−Phosphine Hybrid Ligands for Palladium-Catalyzed Asymmetric Allylic Substitutions

A variety of novel chiral terminal-alkene-phosphine hybrid ligands were successfully developed from diethyl L-tartrate for palladium-catalyzed asymmetric allylic alkylations, etherifications, and amination to give the desired products in excellent yields and ee's.

ChemInform Abstract: Studies on Synthesis of Optically Active Twelve-Membered Diynes: A Convergent Construction of a Twelve-Membered Diketodiyne Compound with C2 Symmetry.

A convergent procedure for the preparation of optically active twelve-membered diketodiyne derivatives with C2 symmetry possessing four hydroxy functionalities was developed starting from the commercially available diethyl L-tartrate. The key step for the construction of the twelve-membered diyne framework involved an intramolecular chromous chloride-mediated coupling reaction between the aldehyde functionality and the alkyne moiety having an iodine atom at its terminus.

Stereoselective Total Syntheses of Three Lycopodium Alkaloids, (−)-Magellanine, (+)-Magellaninone, and (+)-Paniculatine, Based on Two Pauson−Khand Reactions

The total syntheses of (-)-magellanine, (+)-magellaninone, and (+)-paniculatine were completed from diethyl l-tartrate via the common intermediate in a stereoselective manner. The crucial steps in these syntheses involved two intramolecular Pauson-Khand reactions of enynes: the first Pauson-Khand reaction constructed the bicyclo[4.3.0] carbon framework, the corresponding A and B rings of these alkaloids in a highly stereoselective manner, whereas the second Pauson-Khand reaction stereoselectively produced the bicyclo[3.3.0]skeleton, which could be converted into the C and D rings of the target natural products.

Separation of corticosteroids by microemulsion EKC with diethyl L‐tartrate as the oil phase

A novel microemulsion based on a mixture of diethyl L-tartrate (DET) and SDS was developed for the microemulsion EKC (MEEKC) determination of structurally related steroids. The system consisted of 0.5% w/w DET, 1.7% w/w SDS, 1.2% w/w 1-butanol, 89.6% w/w phosphate buffer (40 mM, pH 7.0), and 7% w/w ACN. With an applied voltage of +10 kV, a baseline separation of aldosterone (A), cortisone acetate (CA), dexamethasone (D), hydrocortisone (H), hydrocortisone acetate (HA), prednisolone (P), prednisolone acetate (PA), prednisone (Ps), triamcinolone (T), and triamcinolone acetonide (TA) could be achieved. Under the optimized conditions, the reproducibility of the retention time (n = 4) for most of the compounds was less than +/-0.8% with the exception of A, Ps, and T. The average number of theoretical plates was 18 800 plates/m. The results were compared with those achieved by the modified micellar EKC (MEKC). MEEKC showed obvious advantages over MEKC for the separation of highly hydrophobic substances. To further evaluate the system, we tested the MEEKC method by analyzing corticosteroids in a spiked urine sample.

Spectroscopic Investigation of the Structures of Dialkyl Tartrates and Their Cyclodextrin Complexes

Structures of three dialkyl tartrates, namely, dimethyl tartrate, diethyl tartrate, and diisopropyl tartrate, in CCl4, dimethyl sulfoxide (DMSO)/DMSO-d6, and H2O/D2O solvents have been investigated using vibrational absorption (VA), vibrational circular dichroism (VCD), and optical rotatory dispersion (ORD). VA, VCD, and ORD spectra are found to be dependent on the solvent used. Density functional theory (DFT) calculations are used to interpret the experimental data in CCl4 and DMSO. The trans-COOR conformer with hydrogen bonding between the OH group and the C=O group attached to the same chiral carbon is dominant for dialkyl tartrates both in vacuum and in CCl4. The experimental VA, VCD, and ORD data of dialkyl-D-tartrates in CCl4 correlated well with those predicted for dimethyl-(S,S)-tartrate molecule as both isolated and solvated in CCl4. In DMSO solvent, dialkyl tartrate molecules favor formation of intermolecular hydrogen bonding with DMSO molecules. Clusters of dimethyl-(S,S)-tartrate, with one molecule of dimethyl-(S,S)-tartrate hydrogen bonded to two DMSO molecules, are used for the DFT calculations. A trans-COOR cluster and a trans-H cluster are needed to obtain a reasonable agreement between the predicted and experimental data of dimethyl tartrate in DMSO solvent. VA, VCD, and optical rotations are also measured for dialkyl tartrate-cyclodextrin complexes. It is noted that these properties are barely affected by complexation of dialkyl tartrates with cyclodextrins, indicating weak interaction between tartrates and cyclodextrin. Binding constants of alpha-CD and beta-CD with diethyl L-tartrate in both H2O and DMSO have been determined using isothermal titration calorimetry technique. The smaller binding constants (less than 100) confirmed the weak interaction between tartrates and cyclodextrin in the solution state.

Remarkable effect of hydrogen-bonding interaction on stereospecificity in the radical polymerization of N-vinylacetamide

Radical polymerization of N-vinylacetamide (NVA) in toluene at low temperatures was investigated. It was found that the addition of Lewis bases or alcohol compounds significantly influenced stereospecificity in NVA polymerization. For example, syndiotacticity increased from 25% to 34% by adding tri- n-butyl phosphate at −40 °C. Mono-alcohol compounds increased heterotacticity and heterotactic poly(NVA) with mr triad content of 58% was obtained at −40 °C in the presence of 1,1,1,3,3,3-hexafluoro-2-propanol. Furthermore, isotactic poly(NVA) with mm triad = 49% was obtained at −60 °C in the presence of diethyl l-tartrate. The NMR analysis demonstrated that complex formation between NVA monomer and the added agents, through hydrogen-bonding interaction, played an important role to induce the stereospecificity.

Enantiomerically pure 4-amino-1,2,3-trihydroxybutylphosphonic acids

(1 S,2 R,3 S)-, (1 R,2 R,3 S)- and (1 S,2 R,3 R)-4-amino-1,2,3-trihydroxybutylphosphonic acids were synthesised. The synthetic strategy involved preparation of the respective 4-azido-2,3- O-isopropylidene- l-threose or - d-erythrose, addition of dialkyl phosphites, separation of C-1 epimeric O, O-dibenzyl phosphonates, the reduction of azides and the removal of the protecting groups. The (2 R,3 S) and (2 R,3 R) configurations in the final products were secured by employing diethyl l-tartrate and d-isoascorbic acid as starting materials. The stereochemical course of the addition to the carbonyl groups in 4-azido-2,3- O-isopropylidene- l-threose or - d-erythrose followed that established earlier for 2,3- O-isopropylidene- d-glyceraldehyde and similar (3:1–4:1) diastereoselectivities were achieved.